LG Oven F9 Error Code – Troubleshooting Guide

So, it’s dinner time and you plan to use your LG oven to cook a potion of the meal.

The only problem… The oven is throwing a F9 error code, and you don’t know what to do.

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While you’ll probably have to make other plans for dinner, there are common reasons for this that you can troubleshoot.

The following guide will discuss what the F9 error code is, possible problems, and how to fix them.

What Does the F9 Error Code Mean on My LG Oven?

When the LG oven’s display panel shows the error code F9 it means the oven failed to exceed 150 degrees Fahrenheit after 5 minutes of preheating.

Possible Problems and Solutions For Gas And Electric Oven

Below is a list of common issues and how to fix them. Please note, some of them only pertain to gas model LG ovens.

Faulty Relay Board (most Common)

The relay control board responds to signals sent from the microprocessor display control board in the control panel by opening and closing relays to control the voltage that goes to the burners, elements, and the oven.

So, when the oven relay board is faulty (get a new one here), it can manifest in several ways. This includes turning on, but not heating up as it should.

If you suspect this is your problem, the best thing you can do is test for continuity using a multimeter. If you find there is none, the part will need to be replaced.

This particular relay board located at the bottom right (electric oven) or top right (gas oven), behind the range. You need to pull the range out and remove back panel.

Here’s how to replace this part:

  1. Disconnect the power from the unit
  2. Remove the screws holding the rear access panel brackets in place
  3. Carefully remove each bracket
  4. Remove the screws holding the panel in place
  5. Lift on the panel to detach it
  6. Disconnect the wiring harnesses from the relay board, and remember how they go
  7. Remove the screws holding the board in place
  8. Once the screws are removed, release all retaining clips to detach the old board completely
  9. Install the new board by aligning it correctly into the control assembly and snapping it in place
  10. Follow these steps backward to reassemble your oven

Failed Main PCB

The main PCB, or printed circuit board, is essentially the brain inside your oven. It controls most all the processes that occur.

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This is another problem that can manifest in many ways. One such way is the oven not heating. Once you determine the PCB has failed, here’s how to make the repair:

  1. Disconnect the power and turn off the gas
  2. Remove the screws holding the upper access panel brackets in place
  3. Carefully remove the brackets
  4. Remove the remaining screws holding the access panel in place
  5. Lift on the access panel and remove
  6. Note the orientation of the wires connected to the control board
  7. Detach the ribbon connector and two lower wires
  8. Disconnect the wire from the power supply board and relay board
  9. Remove the mounting screws holding the board to the control assembly
  10. Release retaining clips to detach the old board
  11. Align the new board into the control assembly and snap into place
  12. Follow these steps backward to reassemble your unit

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Thermal Fuse

One common issue with LG ovens is that they can overheat during the cleaning cycle. When this occurs it can damage one of two parts: the thermal fuse or the thermostat.

The thermal fuse is an important component that is designed to blow when your oven tries to go above a certain temperature.

They burn out and stop power to the unit to prevent a house fire.

If your oven got too hot and you think it may be the thermal fuse, it’s best to check this part for continuity with a multimeter.

If this is your problem, you’ll need to replace it.

The good news is that it’s an easy fix and the part is one of the cheaper items.

The Thermostat is another part that’s commonly damaged when the oven overheats after a cleaning cycle.

If the thermostat is bad, it’s usually easy to tell as it will be deformed. If this is the case, here’s how to change it:

  1.  Disconnect the power
  2. Remove the main rear access panel
  3. Locate the thermostat
  4. Remove the two wires attached to the thermostat
  5. Detach the metal tab holding the part in place
  6. Remove and discard the old thermostat
  7. Install the new one and reassemble your unit

Faulty Gas Valve

Your LG oven could begin throwing the F9 error code if the gas valve is faulty. Since the unit is gas powered, it must have gas going to the oven, or it will never heat.

You can use a multimeter to test for continuity. If there is none, follow these steps to replace the gas valve:

  1. Disconnect the power and turn off the gas supply
  2. Remove the screws holding the lower rear access panel in place
  3. Lift the panel up and remove it
  4. Note the location of the broil and bake wires connected to the valve and disconnect them
  5. Release the locking tabs and detach the wires from the back wire terminals
  6. Unthread the nuts securing the gas supply tube to the valve, and replace them
  7. Remove all screws holding the valve to the rear panel
  8. Remove and discard the old valve
  9. Install the new valve by inserting the gas supply tubes into the valve and position the valve onto the mounting tabs
  10. Work backwards to begin reassembling your unit

Failed Igniter

One of the most common causes for an LG gas oven to throw an F9 error code is a bad igniter.

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The igniter is necessary to draw electrical current through the safety valve to heat up and ignite the gas in the oven’s burner.

Once an igniter becomes weak or fails, the gas will not ignite, and the oven won’t heat.

There is an easy check for this. Simply look at the igniter when the oven is turned on. If it glows red for over 90 seconds without igniting the burner, or doesn’t glow at all, it’s failed.

Here’s how to replace this part:

  1. Disconnect the power and turn off the gas supply
  2. Open the oven door
  3. Lift up both hinge stops
  4. Fully remove the oven door
  5. Remove all shelves inside
  6. Remove the screws that secure the oven’s bottom access panel
  7. Lift the bottom panel out
  8. Remove the screws securing the burner shield
  9. Lift the shield off
  10. Unthread the mounting screws that secure the igniter in place
  11. Disconnect the wire connector to remove the old igniter
  12. Install the new igniter
  13. Move backward to assemble your oven

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In conclusion, these repairs are common issues with the LG oven when it shows the F9 error code.

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As you can see most are easy enough to complete on your own.

Has your LG oven displayed the F9 error code in the past?

If so, what part was to blame, and how did you fix it? Leave us a comment and let us know!

4 thoughts on “LG Oven F9 Error Code – Troubleshooting Guide”

    • (Warning! You have to deal with high voltage and there is a chance to be electrocuted!! ) To be exact, you need to check power line IN and OUT on the relay. Relay has 2 wire connectors on the top (IN and OUT) . If you have power on IN, but dont on OUT , that’s mean relay not engaging contacts and not sending power to the heating element.

      Reply
  1. W were getting an error code f9, we watched a YouTube video about the ignitor, pulled it and it was broken. Replaced it and oven worked again, for about 3 days. Now, no heat and f9 error code again! What now?

    Reply

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